One well-known type of extracorporeal blood processing involves an aphaeresis system and procedure in which blood is removed from a donor or a patient (hereafter referred to as a donor), directed to a blood component separation device (e.g., centrifuge), and separated into various blood component types (e.g., red blood cells, white blood cells, platelets, plasma) for collection or therapeutic purposes. Some of these blood component types may either be collected or may be treated for therapeutic purposes and returned to a donor, while the remainder may simply be returned to the donor. Representative centrifugal blood processing systems are the Trima (trademark) and Trima Accel (trademark) apheresis machines available from CaridianBCT. Features of these systems are described in US patents and patent applications including, for example, U.S. Pat. Nos. 7,052,606, and 6,773,413, and 6,200,287, and U.S. application Ser. No. 12/234,960.
A number of factors may affect the commercial viability of an aphaeresis system. One factor relates to the time and expertise required of an individual to prepare and operate the aphaeresis system. For instance, reducing the time required by the operator to complete an entire collection procedure, as well as reducing the complexity of these actions, can increase productivity or lower the potential for operator error. Moreover, reducing the dependency of the system on the operator may further lead to reductions in the credentials desired/required for the operators of these systems. Characteristics of the fluids during the collection process may be sensed by various sensors in order to automate the separation process, as far as possible. An exemplary sensor illuminates a tube transporting fluid and detects ratios of reflected or transmitted red and green light from the fluid. The presence of red blood cells can be detected. Such a sensor is described in U.S. Pat. No. 5,734,464. Nevertheless, accurate and consistent control of a high-speed centrifugal blood separation system is difficult and complex, and further improvement in the control of possible failure modes is desirable.